On 2022-04-19 at 15:34:11 -0700, Reinette Chatre wrote:
Hi Pengfei,
On 4/18/2022 9:31 PM, Pengfei Xu wrote:
On 2022-04-18 at 09:04:33 -0700, Reinette Chatre wrote:
Hi Pengfei,
On 4/16/2022 12:52 AM, Pengfei Xu wrote:
On 2022-03-15 at 09:44:25 -0700, Reinette Chatre wrote:
Some selftests depend on information provided by the CPUID instruction. To support this dependency the selftests implement private wrappers for CPUID.
Duplication of the CPUID wrappers should be avoided.
Both gcc and clang/LLVM provide __cpuid_count() macros but neither the macro nor its header file are available in all the compiler versions that need to be supported by the selftests. __cpuid_count() as provided by gcc is available starting with gcc v4.4, so it is not available if the latest tests need to be run in all the environments required to support kernels v4.9 and v4.14 that have the minimal required gcc v3.2.
Provide a centrally defined macro for __cpuid_count() to help eliminate the duplicate CPUID wrappers while continuing to compile in older environments.
Suggested-by: Shuah Khan skhan@linuxfoundation.org Signed-off-by: Reinette Chatre reinette.chatre@intel.com
Note to maintainers:
- Macro is identical to the one provided by gcc, but not liked by checkpatch.pl with message "Macros with complex values should be enclosed in parentheses". Similar style is used in kernel, for example in arch/x86/kernel/fpu/xstate.h.
tools/testing/selftests/kselftest.h | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
diff --git a/tools/testing/selftests/kselftest.h b/tools/testing/selftests/kselftest.h index f1180987492c..898d7b2fac6c 100644 --- a/tools/testing/selftests/kselftest.h +++ b/tools/testing/selftests/kselftest.h @@ -52,6 +52,21 @@
- have __cpuid_count().
- */
+#ifndef __cpuid_count +#define __cpuid_count(level, count, a, b, c, d) \
- __asm__ __volatile__ ("cpuid\n\t" \
: "=a" (a), "=b" (b), "=c" (c), "=d" (d) \: "0" (level), "2" (count))+#endif
Linux C check tool "scripts/checkpatch.pl" shows an error: " ERROR: Macros with complex values should be enclosed in parentheses
I encountered this also and that is why this patch contains the "Note to maintainers" above. It is not clear to me whether you considered the note since your response does not acknowledge it.
Sorry, I just made a suggestion to fix this problem mentioned by the script. I didn't notice and reply for the note.
... +#define __cpuid_count(level, count, a, b, c, d) \
__asm__ __volatile__ ("cpuid\n\t" \: "=a" (a), "=b" (b), "=c" (c), "=d" (d) \: "0" (level), "2" (count))" Googling: https://www.google.com/search?q=Macros+with+complex+values+should+be+enclose... -> https://stackoverflow.com/questions/8142280/why-do-we-need-parentheses-aroun...
More information available in https://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement-Exprs but from what I understand it does not apply to this macro. Even so, I do not know what checkpatch.pl uses to determine that this is a "Macro with complex values".
Checked checkpatch.pl and it seems to suggest using ({ }) for any asm macro definition.
Could we fix it as follow, shall we? " #ifndef __cpuid_count #define __cpuid_count(level, count, a, b, c, d) ({ \ __asm__ __volatile__ ("cpuid\n\t" \ : "=a" (a), "=b" (b), "=c" (c), "=d" (d) \ : "0" (level), "2" (count)) \ }) #endif "
Sure, I can do so.
I just made a suggestion to fix the problem reported by the checkpatch.pl. But I didn't think deeply enough before: I'm not sure is there any real improvment or help after the fix.
In this case I would prefer to not implicitly follow the checkpatch.pl without understanding what the concern is.
The goal of this change is to make the __cpuid_count() macro available within kselftest and it does so by duplicating gcc's __cpuid_count() macro.
The macro style is not unique and you would, for example, encounter the same checkpatch.pl complaint if you run: ./scripts/checkpatch.pl -f arch/x86/kernel/fpu/xstate.h
Ok, no question from my side.
Thanks! --Pengfei
Reinette